1. Field of the Invention
The present application generally relates to a system and method for providing a wireless system having multiple relays with coordinated operation.
2. Description of the Related Art
A Wireless Distribution System (WDS) is a system that enables the wireless interconnection of access points (AP) in an IEEE 802.11 network. The WDS allows a wireless network to be expanded using multiple access points without the need for a wired backbone to link them, as is conventionally required. The notable advantage of WDS over other solutions is that it preserves the MAC addresses of client packets across links between access points. An access point can be either a main, relay or remote base station. A main base station is typically connected to the wired Ethernet. A relay base station relays data between remote base stations, wireless clients or other relay stations to either a main or another relay base station. A remote base station accepts connections from wireless clients and passes them to relay or main stations. Connections between clients are made using MAC addresses rather than by specifying IP assignments. Typically, nodes in WDS are configured to use the same radio channel. The WDS can be configured to different service set identifiers.
The nodes in a WDS may bridge wireless clients. It should be noted, however, that throughput in this method is traditionally inversely proportional to 2 raised to the power of the number of hops, since all traffic uses the same channel. For example, client traffic going through one relay station before it reaches the main access point in conventional system will see at most half the maximum throughput that a directly connected AP would experience, and a client two hops from the directly connected AP will see at most one quarter of the maximum throughput seen at the directly connected AP. In response to this bandwidth problem, a source node and a relay node may transmit concurrently, and a destination node may be adapted to interpret the combined signals. However, this configuration, as described in greater detail below, also suffers from limitations.
At the same time, wireless communications systems, such as a WDS, typically operate over comparatively short ranges. These limitations in distance are caused by multiple factors. For example, the allowed signal strengths of wireless transmissions are typically low to reduce potential public health risks from the electro-magnetic radiation and to minimize interference with other transmissions. Furthermore, wireless communications typically require substantially line-of-site access between a transmitter and receiver, such that an intermediate structure may block or otherwise attenuate the transmission sufficiently to degrade communications.
Thus, it is known in conventional systems to expand the coverage of a wireless communications network by adding a relay node. However, as described in greater detail below, the conventional relay configuration result in sub-optimal performance due to factors, such as non-uniform signal amplification.